Prediksi Nilai Kuat Lentur Kayu Tropis Berdasarkan Nilai Modulus Elastis

Dalam SNI 7973:2013, nilai modulus elastisitas statik kayu (MoEs) digunakan sebagai dasar pengelompokan mutu kayu. Nilai MoEs juga dapat digunakan untuk memprediksi sifat mekanika kayu yang lain. Penelitian ini melakukan kajian untuk mendapatkan persamaan yang dapat digunakan untuk memprediksi nilai berdasarkan nilai rata rata modulus elastisitas dan persamaan untuk mendapatkan nilai kekuatan lentur (MoR) berdasarkan nilai MoEsnya dari kayu tropis yang ada di Indonesia. Uji lentur statik dilakukan berdasarkan EN 408, sementara itu uji lentur dinamik dilakukan menggunakan metode stress wave velocity. Selain itu, data sekunder hasil pengujian lentur dari para peneliti terdahulu juga digunakan dalam penelitian ini. Dari hasil analisis, nilai adalah sebesar 0,754 dari . Analisis regresi linear menunjukkan bahwa nilai MoR dapat didekati dengan persamaan 𝑀𝑜𝑅 = −1,359 + 0,0061, dimana dari persamaan ini dapat diketahui bahwa nilai desain acuan yang ada pada Tabel 4.2.1 SNI 7973:2013 cenderung memberikan faktor keamanan yang memadai. Pengujian lentur dinamik kayu menunjukkan bahwa hubungan antara modulus elastisitas dinamik (MoEd) dan MoEsdapat didekati melalui persamaan = −1330,1 + 1,254 dengan koefisien determinasi () sebesar 0,69.

Linking Visual and Stress Wave Grading of Beech Wood from the Log to the Sawmill Product

The quality potential and possibilities of using beech logs and sawn wood was investigated. Twenty-seven beech logs, with a mean diameter of 48 cm, were cut from 10 trees from a Hacquetio epipactidis-Fagetum site in SE Slovenia. The trees were pre-selected according to the national 5-level quality scale for forest stand evaluation, using two trees per class. Beech logs were classified according to the EN 1316-1 and sawn afterwards into unedged boards of 35 mm nominal thickness. Altogether, 250 boards were visually graded according to the rules of the European Organisation of the Sawmill Industry (EOS). Longitudinal vibration of logs and boards with the determination of stress wave velocity by MTG timber grader was additionally included into the quality assessment. In the case of logs, we confirmed significance of the relationship between visually assessed log quality and stress wave velocity. The stress wave velocity in logs was also related to the stress wave velocity in boards, where it varied considerably, especially for low-graded material. In the case of sawn wood, the relationship between sawn wood grade and stress wave velocity was insignificant. The research confirmed the possibility of presorting of logs, visually or non-destructively, for better classification and utilization of sawn timber.

Propagation velocity model of stress waves in larch wood (Larix gmelinii) three-dimensional space with different moisture contents

Based on the effects of stress wave propagation in larch (Larix gmelinii) wood, the propagation mechanism of stress wave was explored, and a theoretical model of the propagation velocity of stress waves in the three-dimensional space of wood was developed. The cross and longitudinal propagation velocities of stress wave were measured in larch wood under different moisture contents (46% to 87%, 56% to 96%, 20% to 62%, and 11% to 30%) in a laboratory setting. The relationships between the propagation velocity of stress waves and the direction angle or chord angle with different moisture contents were analyzed, and the three-dimensional regression models among four parameters were established. The analysis results indicated that under the same moisture content, stress wave velocity increased as the direction angle increased and decreased as chord angle increased, and the radial velocity was the largest. Under different moisture contents, stress wave velocity gradually decreased as moisture content increased, and the stress wave velocity was more noticeably affected by moisture content when moisture content was below the fiber saturation point (FSP, 30%). The nonlinear regression models of the direction angle, chord angle, moisture content, and the propagation velocity of stress wave fit the experiment data well (R2 ≥ 0.97).

Utilization potential of naturally regenerated Mongolian Betula platyphylla wood based on growth characteristics and wood properties

To preliminary evaluate the potential wood utilization of Sukaczev trees naturally regenerated in Mongolia, growth characteristics (stem diameter and tree height), wood properties (annual ring width, basic density, and compressive strength parallel to grain at the green condition) of core samples, and stress-wave velocity in stems were investigated for trees grown naturally in three different sites in Selenge, Mongolia. trees, naturally grown in Nikko, Japan, were also examined to compare wood properties between the two regions. The mean values of stem diameter, tree height, stress-wave velocity of stems, annual ring width, basic density, and compressive strength parallel to grain at green condition in Mongolian were 17.6 cm, 14.1 m, 3.50 km s, 1.27 mm, 0.51 g cm, and 20.4 MPa, respectively. Basic density and compressive strength were decreased first from the pith, and then gradually increased toward the bark. The wood properties of trees grown naturally in Mongolia were similar to those in trees grown in Japan. Growth characteristics, especially stem diameter, were positively correlated with the stress-wave velocity of stems and basic density. Early evaluation of basic density in trees is possible by using wood located 2 cm from the pith. Basic density at the position from the 1st to the 15th annual ring from the pith showed significant between-site differences in Mongolian . Based on the results, it is concluded that the wood of trees grown in Mongolia may be used for industrial products as well as those from similar species in other countries.Betula platyphyllaBetula platyphyllaBetula platyphyllaB. platyphylla–1–3B. platyphyllaB. platyphyllaB. platyphyllaB. platyphyllaB. platyphylla

Geographic variations of wood properties of Larix sibirica naturally grown in Mongolia

Geographic variations in growth, stress-wave velocity of stem, dynamic Young’s modulus of stems and logs, annual ring width, latewood percentage and basic density were investigated for (Münchh.) Ledeb. naturally grown in Mongolia. A total of 250 trees with 20 to 30 cm in stem diameter at a height of 1.3 m above ground level were selected from each natural stand in five different provenances in Mongolia. In addition, five trees in each stand were cut for measuring dynamic Young’s modulus of stems and logs, annual ring width, latewood percentage and basic density. Mean values of stress-wave velocity of stems in each stand ranged from 2.92 to 3.41 km s, and the mean value of five stands was 3.23 km s. Mean values of dynamic Young’s modulus of logs in each stand ranged from 5.17 to 9.72 GPa. A significant correlation ( = 0.798,  < 0.01) was found between stress-wave velocity of stems and dynamic Young’s modulus of logs. Among the five stands, the highest and the lowest values of average annual ring number were 193 and 44, respectively. Mean values of basic density in five trees within each stand were examined and ranged from 0.52 to 0.56 g cm. Significant differences among five stands were found in tree height, stress-wave velocity of stem, dynamic Young’s modulus of stems and logs, annual ring width and latewood percentage, suggesting that trees naturally grown in Mongolia have geographic variations in mechanical properties of wood.Larix sibirica–1–1rp–3L. sibirica

Wood Properties of Three Fruit Tree Species Planted in Central Kalimantan, Indonesia

The objective of this study was to evaluate the properties for wood utilization of fruit trees planted in Central Kalimantan, Indonesia. A total of 9 jambu bol (Syzygium malaccense), rambutan (Nephelium lappaceum), and durian (Durio zibethinus) trees were randomly selected from the plot (20 by 30 m) and measured for stem diameter, tree height, stress-wave velocity (SWV), and Pilodyn penetration of the trees. Mean values of stem diameter were 11.8, 15.9, and 29.3 cm for S. malaccense, N. lappaceum, and D. zibethinus, respectively. Mean values of stress-wave velocity were 3.16, 3.95, and 3.63 km/s for S. malaccense, N. lappaceum, and D. zibethinus, respectively. Core samples (5 mm in diameter) were collected from these trees to investigate the wood properties [basic density (BD) and compressive strength parallel to grain (CS)], anatomical characteristics [vessel diameter (VD), cell wall thickness (CWT) in wood fiber, and cell length (CL) of wood fiber and vessel element], and amounts of chemical components. In VD, CWT in wood fiber, and CL in wood fiber and vessel element, almost the same radial variation patterns were found in the three species. Relatively higher values in SWV, BD, and CS were found in N. lappaceum, suggesting that its wood can be used for construction lumber. On the other hand, S. malaccense and D. zibethinus had relatively thicker CWT in wood fiber, longer CL in wood fiber, and lower Klason lignin content. It is considered that the wood of these two species may be suitable for pulpwood.